Uterine flushings from ovariectomized-progesterone treated pigs will be evaluated for collagenase, sulfotransferase, sulfatase protease and protease inhibitor activity. Purification and characterization of leucine aminopeptidaseand lysozyme, previously isolated will be continued. The purple acid phosphatase will be labelled with Fe59 and studies will be conducted to determine whether or not this protein acts to transport iron to fetal and placental tissues. Retenoic acid and retinol binding to porcine uterine proteins will be evaluated. In vitro culture of epithelial cells from procine endometrium will be continued to evaluate effects of progesterone and estrogen on acid phosphatase and leucine aminopeptidase activity. Estrogen effects on synthesis and secretion of total uterine protein, acid phosphatase and prostaglandin F2 alpha will be evaluated in an attempt to determine how estrogen (a luteotrophic substance in swine) prevents corpora lutea regression. Finally, uterine flushings from non-pregnant and pregnant pigs on days 6, 8, 10, 12, 13, 14, 15, 16 and 18 after onset of estrus or mating will be studied to evaluate the effects of pregnancy on porcine uterine protein secretions. These studies will allow us to continue to evaluate the nature and possible roles of progesterone-induced uterine proteins in the pregnant uterus. BIBLIOGRAPHIC REFERENCES: Chen, T. T., Fuller W. Bazer, B. Gebhardt and R. M. Roberts. 1975. Uterine secretion in mammals: Synthesis and placental transport of a purple acid phosphatase in pigs. Biol. Reprod. 13:304-313. Roberts, R. M. and Fuller W. Bazer. 1976. Phosphoprotein phosphatase activity of the progesterone-induced purple glycoprotein of the porcine uterus. Biochem. Biophys. Res. Commun. 68:450-455.